EP0139123B1 - Protective relay system - Google Patents
Protective relay system Download PDFInfo
- Publication number
- EP0139123B1 EP0139123B1 EP84109048A EP84109048A EP0139123B1 EP 0139123 B1 EP0139123 B1 EP 0139123B1 EP 84109048 A EP84109048 A EP 84109048A EP 84109048 A EP84109048 A EP 84109048A EP 0139123 B1 EP0139123 B1 EP 0139123B1
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- EP
- European Patent Office
- Prior art keywords
- value
- sampling time
- power system
- time point
- electric power
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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- 230000001681 protective effect Effects 0.000 title claims description 19
- 238000005070 sampling Methods 0.000 claims description 30
- 238000000034 method Methods 0.000 claims description 15
- 230000001939 inductive effect Effects 0.000 claims description 4
- 230000005540 biological transmission Effects 0.000 description 15
- 230000014509 gene expression Effects 0.000 description 7
- 230000006870 function Effects 0.000 description 6
- 238000010586 diagram Methods 0.000 description 5
- 238000005259 measurement Methods 0.000 description 5
- 238000011045 prefiltration Methods 0.000 description 4
- 230000004044 response Effects 0.000 description 3
- 238000001914 filtration Methods 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- 238000012332 laboratory investigation Methods 0.000 description 1
- 230000001052 transient effect Effects 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/40—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to ratio of voltage and current
Definitions
- the present invention relates to a method for the distance protection of an electric power system comprising the steps of providing signals indicative of successive sampled values of the current and voltage at a relay location of the electric power system, determining or discriminating the value of the inductance L of that portion of the electric power system which lies between the relay location and a fault point, and producing a signal to be used for the protection of the electric power system in accordance with the result of said determination or discrimination.
- An object of the invention is to improve distance measurement, and particularly its frequency characteristic of a protective relay system.
- Fig. 2 is a block diagram illustrating the functions of the operation circuit 7 of performing the above-mentioned operations.
- Adding means 12 and 13 receive the samples v m-1 , v m and i m-1 , im and produce outputs v m +v m - 1 and i m+ i m-1 .
- the arrangement may alternatively be such that the data indicative of the values v n , V n-1 , i n-1 , i n-p-1 and i n+p are also supplied from the memory 12.
- the invention is applicable not only to a situation where, as has been described, the value of the inductance L or L a is first determined and then judgement is made as to whether the determined inductance is within a specified range, but also to a situation where judgement is made whether the inductance is larger or smaller than a predetermined value. Therefore, instead of first determining the inductance L according to the equation (4) and then judging whether or not one may use the following expression to make judgement directly. This is a commonly adopted technique. Still alternatively, the right side of the expression (23) may be a very small positive value, rather than zero, to increase the stability of operation of the relay device. This itself is also a well known technique.
- the determined value of the inductance may be in combination with other value or values to calculate some other quantity, and a signal to be used for protection is produced in accordance with the resultant value of such other quantity.
- the signal to be used for protection may not necessarily be a fault signal for producing an alarm or for tripping a circuit breaker, but may be a signal used in combination with a signal produced as a result of protective relay operation or function of a different type.
Landscapes
- Emergency Protection Circuit Devices (AREA)
- Locating Faults (AREA)
Description
- The present invention relates to a method for the distance protection of an electric power system comprising the steps of providing signals indicative of successive sampled values of the current and voltage at a relay location of the electric power system, determining or discriminating the value of the inductance L of that portion of the electric power system which lies between the relay location and a fault point, and producing a signal to be used for the protection of the electric power system in accordance with the result of said determination or discrimination.
- The invention relates also to a protective relay system for an electric power system.
- Protective relay systems of a distance measurement type are classified into those determining the distance in accordance with an impedance in a steady state and those utilizing a differential equation which holds even in a transient state. The protective relay systems of the former class have been widely adopted for a long time because stable characteristics are obtained. But they have encountered a problem in recent years when distortions in the voltage and current are greater, and filters have to be inserted to remove the distortions and this in turn causes a delay in the response due to delay in the output of the filter. For this reason, the protective relay systems of the latter class are now drawing attentions. Examples of the protective relay system belonging to this class are shown in the following publications:
- i) Japanese Patent Application Publication No. 31747/1978, "A System for Measuring an Impedance Component in an Electric Power System".
- ii) IEEE Paper F77 052-4, W. D. Breingan et al, "The Laboratory Investigation of a Digital System for the Protection of Transmission Lines".
- These systems both determine the inductance L of an electric power system, e.g., a transmission line, by solving a differential equation
- The approximation by the equation (2) has a sufficiently high accuracy as far as the variation in the current i is slow compared with the difference t1-to, i.e., one sampling interval. In other words, a sufficient accuracy is ensured for the fundamental frequency component but the error for the second harmonic or the like is considerable. It is necessary to improve the frequency characteristics in order to attain a sufficiently high accuracy over a wide frequency range without removing the frequency components of these regions by the use of a filter.
- An object of the invention is to improve distance measurement, and particularly its frequency characteristic of a protective relay system.
-
- v represents the voltage,
- i represents the current,
- R represents the resistance,
- t represents the time,
- tk and tk-1 represent time points,
- iklp and ik-p-1 represent values of the current i for time points represented by tk+p and tk-P-1,
- p represents integers (0, 1,... N),
- N represents a natural number,
- Kp (p=0, 1, ... N) represents constants, with at least Ko and K1 being values other than zero and being so determined that the errors in the approximation for the inductance is zero for specified frequencies.
- The method and system of the invention are specified in
claims claims - In the accompanying drawings:
- Fig. 1 is a block diagram showing hardware of a protective relay system of an embodiment of the invention;
- Fig. 2 is a block diagram showing functions of the operation unit of the system of Fig. 1;
- Fig. 3 is a characteristic diagram for comparing the conventional system and the system of the invention; and
- Fig. 4 is a diagram showing another example of the transmission line for which the protective relay system according to the invention can be used.
- Referring now more particularly to Fig. 1, there is shown a hardware structure of the protective relay system in connection with a
transmission line 1, forming an example of electric power system to be protected by the protective relay system. The protective relay system comprises avoltage transformer 2 and acurrent transformer 3 respectively detecting the voltage and the current of the transmission line, which is, in the case under consideration, assumed to be a single-phase line for the purpose of simplicity of explanation. Aninput converting circuit 4 receives the output of thetransformer 2 and converts it into a signal of a suitable level, and comprises a pre-filter for removing high frequency components. The output v of the pre-filter constitutes the output of theinput converting circuit 4. Theinput converting circuit 4 having such functions can be constructed in a known manner, so that details thereof will not be described here. Aninput converting circuit 5 is similar to theinput converting circuit 4. It receives the secondary current of thecurrent transformer 3 and converts it into a voltage signal of a suitable level, and comprises a pre-filter for removing high frequency components. The output i of the pre-filter constitutes the output of theinput converting circuit 5. The reference characters v and i are also used to denote the voltage and the current of thetransmission line 1. - An
AD converting circuit 6 simultaneously samples the output v of theinput converting circuit 4 and the output i of theinput converting circuit 5 at regular intervals and digitizes the sampled values to provide digital signals indicative of the instantaneous values of the voltage v and the current i. TheAD converting circuit 6 having such functions can be constructed in a known manner, so that the details thereof will not be described here. The digital signals or the data from the AD converting circuit are stored in adata memory 12. Thus the data stored in thememory 12 form time series of data indicative of the instantaneous values vk, ik of the voltage and the current, with k representing the sampling time points as expressed by the consecutive integers. - An
operation unit 7 may for example be formed of a computer, such as a microcomputer, and performs arithmetic operations, judgements, and input/output operations normally required of a protective relay system, but such functions are realized in a known manner utilizing known techniques, so that details thereof will not be described here. Theoperation unit 7 also performs the following arithmetic operation to determine the inductance L of that portion of the electric power system which lies between the relay location and the fault point. - vk (k=n, n-1, m or m-1) and ik (k=n, n-1, m, m-1, n+p, n-p-1, m+p, or m-p-1) represent the values of the voltage and the current at the respective time points k,
- n and m represent sampling time points as expressed by respective one of consecutive integers, with n and m differing from each other,
- p represents integers, 0, 1,... N,
- N represents a predetermined natural number,
- Kp (p=0, 1, ... N) represents a constant, with at least Ko and K, being values other than zero and being so determined, in a manner described later, that the errors in the approximation for the inductance is zero for specified or selected frequencies.
- The
operation unit 7 also performs judgement in accordance with the value of L determined according to the above equation. - Fig. 2 is a block diagram illustrating the functions of the
operation circuit 7 of performing the above-mentioned operations. - Adding means 12 and 13 receive the samples vm-1, vm and im-1, im and produce outputs vm+vm-1 and im+im-1.
-
-
- A multiplying
unit 18 receives and multiplies vn+vn-1 and im+im-1 and produces an output expressed by the first term of the numerator of the equation (4). A multiplyingunit 19 receives and multiplies vm+vm-1 and in+in-1 and produces an output expressed by the second term of the numerator of the equation (4). A multiplyingunit 20 receives and multiplies in+in-1 andunit 21 receives and multiplies im+im-1 and - A subtracting
unit 22 subtracts the output of theunit 19 from the output ofunit 18 to determine a value expressed by the numerator of the equation (4). A subtractingunit 23 subtracts the output of theunit 20 from the output ofunit 21 to determine a value expressed by the denominator of the equation (4). A dividingunit 24 divides the output of theunit 22 by the output of theunit 23 to determine the value expressed by the entirety of the equation (4), i.e., the inductance L. - The signal indicative of the inductance L thus determined is applied to a
discriminator 26 which produces a fault signal if the inductance L is found to be within a specified range. The fault signal is used for producing an alarm, or for tripping a circuit breaker, not shown, provided at the relay location to protect the transmission line, or is used in combination with a signal produced as a result of protective relay operation of different type. - In the example described with reference to Fig. 2, the data indicative of the values vm, vm-1, im, im-1, im-p-1 and im+p are derived from the
data memory 12, while the data indicative of the values vn, vn-1, in, in-1, in-p-1 and in+p are produced by the use of delay means within theoperation unit 7 from the data supplied from thememory 12. - However, the arrangement may alternatively be such that the data indicative of the values vn, Vn-1, in-1, in-p-1 and in+p are also supplied from the
memory 12. - Now explanation as to why the incorporation of the approximate expression (3) in the equation (1) leads to the equation (4), and why the use of the approximate expression (3) ensures a high accuracy will be given. From the equation (1), we obtain,
- If we substitute the equations (8) and (9) in the equations (6) and (7), we will obtain the equation (4).
- Fig. 3 shows the performance or the accuracy of the system of the invention and a conventional system. The
solid lines 8 and 9 illustrate two examples of error versus frequency characteristics of inductance measurement according to the invention, while thebroken line 10 illustrates an example of error versus frequency characteristics of inductance measurement of a conventional system. It will be seen that the system according to the invention has much smaller errors over a wide range of frequency than the conventional system. This means that the system of the invention is less affected by waveform distortion. This will be explained next. - The true value Lt of the inductance, which is obtained by solving the equations (6) and (7) without using the approximation of the expressions (8) and (9), is given by:
-
- The
solid line 8 in Fig. 3 represents an example where ω1T=30°, ω2/ω1=2, while the solid line 9 represents an example where ω1T=30°, ω2/ω1=3. If ω1 is the fundamental angular frequency, ε is zero at the fundamental frequency and at a frequency twice the fundamental frequency with the former example, while e is zero at the fundamental frequency and at a frequency three times the fundamental frequency with the latter example. In each case, the error ratio is very small in the area proximate to the frequency where s=0. - In contrast, the conventional system uses the approximation of the equation (2) so that the error ratio is 0 at ω=0 and the error ratio e increases with the angular frequency w. The
broken line 10 in Fig. 3 represents an example where ω1T=30°. - It has been assumed that Ko and K1 are other than zero and K2, K3, K4, etc., are zero. But if K2, K3, K4, etc. are also set to be a value, to make s=0 at respective frequencies, the frequency characteristic is further improved. However, with a larger number of Kp which are not zero, it takes a longer time for calculation and delay in response becomes longer. Accordingly, a compromise must be made between a higher accuracy and a quick response. It has however been found that using two non-zero constants Ko, K1 to obtain s=0 at two frequencies yields practically satisfactory results.
- In describing the embodiment of Fig. 1, the
transmission line 1 is assumed to be a single-phase transmission. This is to facilitate explanation and understanding of the invention. But the invention is also applicable to protection of a multiple-phase e.g., three-phase, transmission line. For instance, two-phase fault in a three-phase transmission line can be dealt with in a manner similar to that adopted'with the single-phase transmission line if one uses the line voltage and the delta current, as will be understood from a well known theory. - Fig. 4 shows a three-
phase transmission line 11 which can be protected by a protective relay system of another embodiment of the invention. As is seen, a three-phase transmission line including lines of phases a, b and c is shown to have a single-line grounding fault F in the phase a. If the voltage at the location where the protective relay system is provided is denoted by v, and the currents of the respective phases a, b and c are denoted by ia, ib and ic, the following equation, which itself is well known, holds: - ra represents a resistive component of the self-impedance,
- rab and rac represent resistive components of the mutual-impedance,
- La represents an inductive component of the self-impedance,
- Lab and Lac represent inductive components of the mutual-impedance,
- i'a, i'b, i'c and j' denote time differentials of ia, ib, ic and j, respectively, as described earlier in this specification.
- The equation (19) can be solved in a similar manner as with the equation (4) as to La and the following equation is derived.
- The invention is applicable not only to a situation where, as has been described, the value of the inductance L or La is first determined and then judgement is made as to whether the determined inductance is within a specified range, but also to a situation where judgement is made whether the inductance is larger or smaller than a predetermined value. Therefore, instead of first determining the inductance L according to the equation (4) and then judging whether or not
- It should therefore be understood that the invention embraces any method or system in which the inductance is measured or discriminated according to the concept expressed by the equations described or any equivalent equations.
- Instead of having a fault signal produced solely in accordance with the result of the determination of the inductance, the determined value of the inductance may be in combination with other value or values to calculate some other quantity, and a signal to be used for protection is produced in accordance with the resultant value of such other quantity.
- The signal to be used for protection may not necessarily be a fault signal for producing an alarm or for tripping a circuit breaker, but may be a signal used in combination with a signal produced as a result of protective relay operation or function of a different type.
- The principle of the invention described with reference to the expressions (19), (20), (21), with which it was assumed that the synthetic values are of different types of electric quantities, e.g., the currents of the different phases ia, ib, ib, is also applicable to a situation where the synthetic values are of the same type of electric quantities. For instance, if synthetic values uk and wk are defined as:
- As has been described, according to the invention, a greater number of sample values are used for the approximation of differentials, and thereby the frequency characteristic of the distance measurement is improved.
Claims (10)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP58144988A JPS6039312A (en) | 1983-08-10 | 1983-08-10 | Protective relaying device |
JP144988/83 | 1983-08-10 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0139123A1 EP0139123A1 (en) | 1985-05-02 |
EP0139123B1 true EP0139123B1 (en) | 1988-05-11 |
Family
ID=15374861
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP84109048A Expired EP0139123B1 (en) | 1983-08-10 | 1984-07-31 | Protective relay system |
Country Status (4)
Country | Link |
---|---|
US (1) | US4577254A (en) |
EP (1) | EP0139123B1 (en) |
JP (1) | JPS6039312A (en) |
DE (1) | DE3471209D1 (en) |
Families Citing this family (14)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS60180424A (en) * | 1984-02-28 | 1985-09-14 | 三菱電機株式会社 | Shorting distance relay |
JPH0828934B2 (en) * | 1984-07-31 | 1996-03-21 | 株式会社東芝 | Protection control device |
JPS61112527A (en) * | 1984-11-07 | 1986-05-30 | 三菱電機株式会社 | Digital distance relay |
JPS6240019A (en) * | 1985-08-13 | 1987-02-21 | 三菱電機株式会社 | Digital distance relay system |
AU603871B2 (en) * | 1987-03-03 | 1990-11-29 | Mitsubishi Denki Kabushiki Kaisha | Digital locator |
SE459946B (en) * | 1987-12-29 | 1989-08-21 | Asea Ab | RELAY PROTECTION WITH SELECTIVE PHASE SELECTION FOR DOUBLE CABLES |
US5483462A (en) * | 1990-05-07 | 1996-01-09 | Cornell Research Foundation, Inc. | On-line method for determining power system transient stability |
JP3119541B2 (en) * | 1993-03-25 | 2000-12-25 | 株式会社東芝 | Frequency detection method |
US5506789A (en) * | 1993-10-15 | 1996-04-09 | The Texas A & M University System | Load extraction fault detection system |
JP3790053B2 (en) | 1998-10-14 | 2006-06-28 | 株式会社東芝 | Distance relay |
AT408921B (en) * | 1999-04-13 | 2002-04-25 | Lothar Dipl Ing Dr Tec Fickert | MEASURING SYSTEM FOR REMOTELY MEASURING CURRENT AND VOLTAGE IN ELECTRIC POWER NETWORKS |
GB201102031D0 (en) * | 2011-02-07 | 2011-03-23 | Rolls Royce Plc | Protection system for an electrical power network |
CN102645614A (en) * | 2012-04-26 | 2012-08-22 | 郭振威 | Transmission line directional element based on high frequency sub-band signal handling capacity difference value of filter bank |
CN104125595B (en) * | 2013-04-25 | 2018-05-11 | 华为技术有限公司 | Fault location and the method and detection device of isolation |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS52100149A (en) * | 1976-02-18 | 1977-08-22 | Tokyo Electric Power Co Inc:The | Digital failure point evaluating unit |
JPS595220B2 (en) * | 1976-09-07 | 1984-02-03 | カルプ工業株式会社 | resin composition |
JPS5592514A (en) * | 1978-12-28 | 1980-07-14 | Tokyo Shibaura Electric Co | Digital protection relay |
JPS55127829A (en) * | 1979-03-27 | 1980-10-03 | Tokyo Shibaura Electric Co | Digital distance relay unit |
US4300182A (en) * | 1979-08-09 | 1981-11-10 | Schweitzer Edmund O Iii | Metering and protection system for an A.C. power system |
-
1983
- 1983-08-10 JP JP58144988A patent/JPS6039312A/en active Granted
-
1984
- 1984-07-31 DE DE8484109048T patent/DE3471209D1/en not_active Expired
- 1984-07-31 EP EP84109048A patent/EP0139123B1/en not_active Expired
- 1984-08-06 US US06/637,722 patent/US4577254A/en not_active Expired - Lifetime
Also Published As
Publication number | Publication date |
---|---|
DE3471209D1 (en) | 1988-06-16 |
US4577254A (en) | 1986-03-18 |
JPS6039312A (en) | 1985-03-01 |
EP0139123A1 (en) | 1985-05-02 |
JPH0320969B2 (en) | 1991-03-20 |
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